Harukichi iwata



March 1964 HARUKICHI IWATA SPRAY NOZZLE FOR AIRLESS SPRAY Filed Oct. 25, 1962 "Inn I INVENTOR United States Patent 3,125,298 SPRAY NOZZLE FOR AIRLESS SPRAY Harultichi Iwata, Tokyo, Japan, assignor to Iwata Tos'oki Kogyo Kabushiki Kaisha, Tokyo, Japan Filed Oct. 23, 1962, Ser. No. 232,378 3 Claims. (Cl. 239-543) This invention relates to a novel improved spray nozzle for airless spray guns.

The conventional paint coating method employed heretofore is to coat the articles with atomized particles in the form of liquid with the help of the energy of the atomized particles or of jetted compressed air simultaneously with atomizing liquid paint mechanically by means or" centrifugal force due to liquid pressure or compressed air.

The atomizing method which uses liquid pressure in the above described coating method is more advantageous than the method which uses compressed air in that it is not injurious to health because it reduces the volume of atomized particles which are scattered due to the disturbance by air, and, also, it is more efiicient since the coating material is saved.

However, the airless spray method utilizing liquid pressure has a great defect in the spray nozzle which is essential to the spraying. In other words, the spray nozzle of the conventional airless spray apparatus has one nozzle hole from which paint is ejected and sprayed, and the shape of such hole must be oval. However, such a nozzle hole has many defects as mentioned below. Although such hole must be made with great precision by an exacting process, the defects in paint coating, such as the so-called tail or uneven mist, occur with a change of coating material. Moreover, even when a super hard substance such as sapphire or tungsten carbide is used as a nozzle material, the life of the nozzle is short and, particularly, the nozzle may become unusable in about 500 hours when some special coating material is used. The above defects of the one-hole spray nozzle are due to the fundamental construction of the nozzle; and the nozzle itself is the major cause of tail, uneven mist and abrasion.

In order to eliminate the defects involved therein, the method of effecting the above spray action outside of the nozzle itself was adopted instead of the method of decreasing the jet velocity or of making the shape into an oval or rectangular pattern in the inner part of the mechanism nozzle, with the result that the larger parts of the defects in the prior art nozzles were eliminated.

This invention relates to a spray nozzle for paint coating, comprising a pair of outwardly angled arms extending in substantially opposite directions from a nozzle cap and having tubular bores extending therethrough. Nozzle tips are provided on the end of each arm and are connected to the bore in the arm, and the nozzle tips have a hole therein which is off-set a little from the center of the end of the nozzle tip. The nozzle tips are rotatable about an axis through the center of the end thereof, and they are inwardly angled toward a common point which is substantially equidistant from each nozzle tip.

One object of the present invention to to reduce the abrasion due to the resistance in the Wall-surface when the coating material is ejected from the small holes by the liquid pressure. In other words, by making the two small holes circular holes, it is possible to remove the edge present in the conventional oval hole, thereby reducing the abrasion due to a lesser resistance in the wallsurface.

Another object of the present invention is to permit a larger tolerance in the dimensions of the nozzle structure. In other words, the locations of the two small holes are made adjustable so that the axes of the holes can cross at a suitable angle.

Still another object of the present invention is to remove the defects, such as tail and uneven mist, which become an obstacle to the coating. The conventional nozzle has the defect in the nozzle construction itself, whereas, under the present invention, it is easy to make the distribution of the groups of the sprayed particles uniform because the atomization is made to occur outside of the nozzle. Also the eiiect obtained by the present invention is that the coated surface is finished such that it is very pretty as compared with the coated surface produced by a conventional nozzle since the diameter of the sprayed particle is smaller at the same jet pressure.

Now the construction according to the present invention will be described with reference to the illustrated embodiments in the accompanying drawing wherein,

FIG. 1 is a side view of the spray gun according to the present invention,

FIG. 2 is a detailed view of the pointed portion of FIG. 1, and

FIG. 3 is an enlarged sectional view of the pointed nozzle tip attached to the nozzle cap.

Referring now to the figures of the accompanying drawing, FIG. 1 shows the preferred example of the present invention and FIG. 2 is a sectional view of the pointed portion.

In the drawing, when the needle valve 11 is opened by pulling the trigger 12, the coating material is forced by a superatmospheric pressure of several atmospheres which is produced by a pressure increasing apparatus (not shown in the drawing) through the needle valve seat 13, which is made of a super-hard substance, from the hole in paint outlet 10, the dust or the lumps in the coating material being filtered by paint filter net 4, and, through the two tubular bores 6 placed in the substantially diammetrically oppositely extending angled arms 6' on cap 14. The coating material is forced out through small holes 2 in nozzle pieces 2 in the inwardly angled nozzle tips 5, which nozzle pieces are made of super hard material such as sapphire or tungsten carbide. Nozzle tips 5 are at the ends of arms 6'. The streams of coating material collide with each other at the center position 30 or in the vicinity thereof and are atomised, and thus the oval or rectangular patterns of fine-grained and uniform particles are obtained.

Since the position of the small holes 2 in the nozzle piece made of sapphire or tungsten carbide, etc. as shown in FIG. 3 is offset a little from the center of the nozzle pieces 2 in nozzle tip 5, it the streams from holes 2 do not meet correctly because of an error in manufacture, each nozzle tip 5 is threaded into the end of an arm 6 so it can be adjusted by the revolution of the nozzle tip 5 so that the streams of coating material meet correctly. Also in order to permit rotating of the nozzle tip 5, elastic packing 15 is provided between nozzle tip 5 and arm 6 and it prevents leakage of coating materials.

Cap 14 and cap cover 8 are separable and cap 14 can be revolved by loosening the cap 8 a little, and, also, by revolving the cap 14, the position of the spray pattern can be changed to the horizontal direction or to the vertical direction.

The shape of two small holes 2 offset a little from the center of nozzle piece 2 in nozzle tip 5 must be the same and it is preferable that the accuracy of processing thereof be as great as possible.

The stream of paints is a stream like a rod and not atomised until they collide. The velocity of these streams vary according to the pressure of the paint, and the velocity is calculated to be about 60 m./ s. under a pressure of 60 kg./cm. The shorter the distance from nozzle tip 5 to the cross and collison point or center position 30, the better the effect of spray due to collision. However, in that case, the preferable effect is not obtained because a tail or uneven mist often appears. The collision point 30 must be placed at the same distance from the two nozzle tips 5. However, with the present invention, a minor error in distance does not cause an adverse effect in the spray condition. In case the distance to the collision point 30 is over mm, an error of several millimeters is allowed. Also, the more obtuse the crossing angle is, the finer becomes the sprayed particles and the wider becomes the pattern. However, in case the said angle is excessively obtuse, the volume of sprayed particle groups which fly about in different directions is increased and the flying velocity of sprayed particle groups is too slow, so that the preferable effect of a general spray for paint coating is not produced. If the pressure of the paint is high, the sprayed particles become fine, and for the general coating, a pressure of 60 kg/cm. is used. The diameter of the two small holes 2 offset a little from the center of the nozzle piece 2 in the nozzle tip 5 is 0.20.4 mm. for general coating. However, a size different from this can be selected according to the operation efficiency and the shape of the goods to be coated. Also, the angle 3 is not specially fixed, but, for general coating, it is preferably selected within the range from 50120 according to the operation etficiency, the shape of goods to be coated and the kind of paint to be used.

The above description is a mere illustration of a certain preferred embodiment of the present invention, and, therefore, it is apparent that various changes of omissions of the form and arrangement of the component part as shown and described herein can be made, as desired, without departing from the spirit and the scope of the present invention as defined in the appended claims.

What I claim is:

1. A spray nozzle for a liquid pressure spray gun, said spray nozzle comprising a nozzle cap having two outwardly angled arms extending in substantially opposite directions, said arms having tubular bores therein extending to the adjacent the ends of said arms, an inwardly angled nozzle tip on the end of each arm and connected to the bore in the arm, said nozzle tips each having a hole therein offset a little from the center of the end of the nozzle tip and said nozzle tips being rotatable about an axis through the center of the end thereof, the nozzle tips being inwardly angled toward a common point substantially equidistant from each nozzle tip, whereby the nozzle tips can be rotated to cause streams of liquid coming through the holes under pressure to collide substantially at said common point and atomise.

2. A spray nozzle as claimed in claim 1 in which each nozzle tip has a nozzle piece in the end thereof in which said hole is positioned, said nozzle pieces being of a super-hard material, and said nozzle tips being threaded into the ends of said arms.

3. A spray nozzle as claimed in claim 1 in which the axes through the centers of said nozzle tips intersect at an angle of from -120".

References Cited in the file of this patent UNITED STATES PATENTS 1,050,338 Carroll Ian. 14, 1913 2,754,151 Williamson July 10, 1956 2,785,926 Lataste Mar. 19, 1957 2,930,532 Johnson Mar. 29, 1960 3,018,968 Levey Jan. 30, 1962 3,062,454 Cocks Nov. 6, 1962 

1. A SPRAY NOZZLE FOR A LIQUID PRESSURE SPRAY GUN, SAID SPRAY NOZZLE COMPRISING A NOZZLE CAP HAVING TWO OUTWARDLY ANGLED ARMS EXTENDING IN SUBSTANTIALLY OPPOSITE DIRECTIONS, SAID ARMS HAVING TUBULAR BORES THEREIN EXTENDING TO THE ADJACENT THE ENDS OF SAID ARMS, AN INWARDLY ANGLED NOZZLE TIP ON THE END OF EACH ARM AND CONNECTED TO THE BORE IN THE ARM, SAID NOZZLE TIPS EACH HAVING A HOLE THEREIN OFFSET A LITTLE FROM THE CENTER OF THE END OF THE NOZZLE TIP AND SAID NOZZLE TIPS BEING ROTATABLE ABOUT AN AXIS THROUGH THE CENTER OF THE END THEREOF, THE NOZZLE TIPS BEING INWARDLY ANGLED TOWARD A COMMON POINT SUBSTANTIALLY EQUIDISTANT FROM EACH NOZZLE TIP, WHEREBY THE NOZZLE TIPS CAN BE ROTATED TO CAUSE STREAMS OF LIQUID COMING THROUGH THE HOLES UNDER PRESSURE TO COLLIDE SUBSTANTIALLY AT SAID COMMON POINT AND ATOMISE. 